Re: Depth buffer vs back-to-front sorting?

From: Angus Dorbie (dorbie++at++sgi.com)
Date: 02/29/2000 17:21:16

• Previous message: Scott Herod: "Depth buffer vs back-to-front sorting?"
• In reply to: Scott Herod: "Depth buffer vs back-to-front sorting?"

The Performer method is more accurate for the general case.
It seems that you have a contrived example in mind where your test
produces better results, (planes parallel to eye space planes of equal
z) but for the general case of flying through a complex world the range
method is better.

For instance your method would be desirable for sorting trees which were
billboarded to the channel forward viewing vector, the Performer method
is better for sorting billboarded trees which billboard to a local
viewer vector to each individual tree.

Unfortunately it is not an option for you to change this, the sort is an
internal Performer algorithm.

Cheers,ANgus.

Scott Herod wrote:
>
> Hello,
>
> I have another question about drawing order and the relationship
> to the depth buffer. If I have a symmetric, prospective pfChannel
> and draw a rectangular geoset that is perpindicular to the frustum's
> axis, the depth buffer is filled with a rectangle of constant
> values. ( It's easy to check and is essentially similar triangles. )
>
> On the other hand, depth sorting of transparent geosets seems to
> be done by computing the Euclidean distance between the centers of
> the geosets' bounding spheres and the eye-point.
>
> Why isn't depth sorting of geosets computed so that iso-surfaces
> are planes parallel to the front and rear clipping planes as is the
> case for filling the depth buffer rather than concentric spheres?
> Is is easy to change the sorting algorithm?
>
> Thank you.
>
> Scott Herod
> herod++at++rtset.com
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-- 
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have taken to raiding 15 year old kids in their bedrooms. Very sad.

• Previous message: Scott Herod: "Depth buffer vs back-to-front sorting?"
• In reply to: Scott Herod: "Depth buffer vs back-to-front sorting?"

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